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|
use std::{
cmp,
io::{self, BufRead, BufReader, Read},
pin::Pin,
task::{self, Poll},
};
use anyhow::{bail, Result};
use bytes::{Buf, Bytes};
use futures::{future::BoxFuture, Future, FutureExt, Stream, StreamExt};
use lazy_static::lazy_static;
use tokio::runtime::Handle;
use nix_compat::nixbase32;
use rusoto_core::{ByteStream, Region};
use rusoto_s3::{GetObjectOutput, GetObjectRequest, S3Client, S3};
use bzip2::read::BzDecoder;
use xz2::read::XzDecoder;
lazy_static! {
static ref S3_CLIENT: S3Client = S3Client::new(Region::UsEast1);
}
const BUCKET: &str = "nix-cache";
pub async fn nar(
file_hash: [u8; 32],
compression: &str,
) -> Result<Box<BufReader<dyn Read + Send>>> {
let (extension, decompress): (&'static str, fn(_) -> Box<_>) = match compression {
"bzip2" => ("bz2", decompress_bz2),
"xz" => ("xz", decompress_xz),
_ => bail!("unknown compression: {compression}"),
};
Ok(decompress(
FileStream::new(FileKey {
file_hash,
extension,
})
.await?
.into(),
))
}
fn decompress_xz(reader: FileStreamReader) -> Box<BufReader<dyn Read + Send>> {
Box::new(BufReader::new(XzDecoder::new(reader)))
}
fn decompress_bz2(reader: FileStreamReader) -> Box<BufReader<dyn Read + Send>> {
Box::new(BufReader::new(BzDecoder::new(reader)))
}
struct FileStreamReader {
inner: FileStream,
buffer: Bytes,
}
impl From<FileStream> for FileStreamReader {
fn from(value: FileStream) -> Self {
FileStreamReader {
inner: value,
buffer: Bytes::new(),
}
}
}
impl Read for FileStreamReader {
fn read(&mut self, dst: &mut [u8]) -> io::Result<usize> {
let src = self.fill_buf()?;
let n = cmp::min(src.len(), dst.len());
dst[..n].copy_from_slice(&src[..n]);
self.consume(n);
Ok(n)
}
}
impl BufRead for FileStreamReader {
fn fill_buf(&mut self) -> io::Result<&[u8]> {
if !self.buffer.is_empty() {
return Ok(&self.buffer);
}
self.buffer = Handle::current()
.block_on(self.inner.next())
.transpose()?
.unwrap_or_default();
Ok(&self.buffer)
}
fn consume(&mut self, cnt: usize) {
self.buffer.advance(cnt);
}
}
struct FileKey {
file_hash: [u8; 32],
extension: &'static str,
}
impl FileKey {
fn get(
&self,
offset: u64,
e_tag: Option<&str>,
) -> impl Future<Output = io::Result<GetObjectOutput>> + Send + 'static {
let input = GetObjectRequest {
bucket: BUCKET.to_string(),
key: format!(
"nar/{}.nar.{}",
nixbase32::encode(&self.file_hash),
self.extension
),
if_match: e_tag.map(str::to_owned),
range: Some(format!("bytes {}-", offset + 1)),
..Default::default()
};
async {
S3_CLIENT
.get_object(input)
.await
.map_err(|e| io::Error::new(io::ErrorKind::Other, e))
}
}
}
struct FileStream {
key: FileKey,
e_tag: String,
offset: u64,
length: u64,
inner: FileStreamState,
}
enum FileStreamState {
Response(BoxFuture<'static, io::Result<GetObjectOutput>>),
Body(ByteStream),
Eof,
}
impl FileStream {
pub async fn new(key: FileKey) -> io::Result<Self> {
let resp = key.get(0, None).await?;
Ok(FileStream {
key,
e_tag: resp.e_tag.unwrap(),
offset: 0,
length: resp.content_length.unwrap().try_into().unwrap(),
inner: FileStreamState::Body(resp.body.unwrap()),
})
}
}
macro_rules! poll {
($expr:expr) => {
match $expr {
Poll::Pending => {
return Poll::Pending;
}
Poll::Ready(value) => value,
}
};
}
impl Stream for FileStream {
type Item = io::Result<Bytes>;
fn poll_next(self: Pin<&mut Self>, cx: &mut task::Context) -> Poll<Option<Self::Item>> {
let this = self.get_mut();
let chunk = loop {
match &mut this.inner {
FileStreamState::Response(resp) => match poll!(resp.poll_unpin(cx)) {
Err(err) => {
this.inner = FileStreamState::Eof;
return Poll::Ready(Some(Err(err)));
}
Ok(resp) => {
this.inner = FileStreamState::Body(resp.body.unwrap());
}
},
FileStreamState::Body(body) => match poll!(body.poll_next_unpin(cx)) {
None | Some(Err(_)) => {
this.inner = FileStreamState::Response(
this.key.get(this.offset, Some(&this.e_tag)).boxed(),
);
}
Some(Ok(chunk)) => {
break chunk;
}
},
FileStreamState::Eof => {
return Poll::Ready(None);
}
}
};
this.offset += chunk.len() as u64;
if this.offset >= this.length {
this.inner = FileStreamState::Eof;
}
Poll::Ready(Some(Ok(chunk)))
}
}
|
